diesel today Rolling Smokestacks: Cleaning Up America s Trucks and Buses

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1 1 C H A P T E R 1 diesel today From the school buses picking up our children to the freight trucks delivering groceries to our supermarkets, the 3.3 million diesel trucks and buses on American roads are the workhorse of the transportation economy. They are used in applications that require power, efficiency, and longevity, and many engines last over one million miles. Unfortunately, these same durable trucks come with a price tag in the form of air pollution, threats to public health, and contribution to global warming. Diesel trucks come in a wide variety of weights and sizes, ranging from lighter diesel trucks like parcel delivery vans, to transit buses, to the heavy big-rigs that transport goods around the country. Table 1 shows the range of vehicles and how they are classified. The heaviest vehicles account for the majority of the miles traveled by trucks each year (Figure 1, next page) and therefore account for the majority of pollution and energy use. But light and medium trucks, as well as urban buses, are significant contributors to pollution, especially in cities where people and diesel pollution are concentrated. The study reported here examines how current and emerging technologies could be employed to limit diesel exhaust, thereby decreasing the public health threat it poses. In this section, we discuss the impacts on public health and global warming of exhaust from today s diesel trucks and buses. The second section describes technologies that could make diesel engines run cleaner. The third section looks at how truly green technologies alternative

2 2 UNION OF CONCERNED SCIENTISTS fuels such as natural gas and advanced technologies such as hybrids and fuel cells are now or could soon replace diesel in various niches. The fourth section discusses which technology might best be employed for each type of vehicle and what national benefits might be expected from conversion to these technologies. The final section suggests how government regulation might help put these technologies on the street. The Need for Cleaner Trucks Today s big-rigs are like rolling smokestacks, emitting three times more soot and smog-forming pollution than a coal-fired power plant, for every unit of energy they burn. 1 Trucks and buses make up less than 2 percent of highway vehicles, and they travel less than 6 percent of the total miles driven each year. Yet they are the source of a quarter of the smog-forming pollutants and over half of the soot from all highway vehicles (Figure 2). 1 National average emissions rate, measured in pollution per unit of energy consumed. UCS calculation based on (a) national emissions inventory (EPA 1997b), adjusted to reflect extra emissions due to defeat devices, and (b) national energy use (EIA 2000).

3 3 While big trucks have faced tougher tailpipe rules over time, these regulations are far more lenient than those imposed on cars, so that much less progress has been made in controlling pollution from big diesel. For example, a car purchased today must emit 23 times less smog-forming pollutants (hydrocarbons plus nitrogen oxides) during emissions testing than an unregulated car did in the 1960s (Hwang 1997). A new big-rig must be only 3 times cleaner for these pollutants than before emission controls were required. New standards already on the books will force both cars and heavy trucks to become cleaner starting in But these rules will once again require more of cars than trucks. As a result, even the cleanest diesel trucks will still emit nearly 10 times more smog-forming pollutants per mile and over 100 times more soot than new passenger vehicles. And because trucks average nearly 4 times more miles per year than do cars, annual emissions from a new truck will continue to be much larger than from a car in the future (Figure 3). The leniency of regulations on diesel trucks and buses comes at a price. Diesel exhaust takes a toll on public health, particularly in cities where the concentration of people and diesel fumes is greatest. And we are all beginning to feel the effects as carbon emissions fuel climate change, bringing heat waves, droughts, floods, and other severe weather in its wake. Public Health Risks Diesel exhaust poses a substantial threat to public health. It can cause or aggravate a variety of respiratory diseases, and it has been linked to cancer.

4 4 UNION OF CONCERNED SCIENTISTS Urban Ozone (Smog) Diesel trucks and other motor vehicles emit nitrogen oxides (NO x ) and hydrocarbons, which contribute to ozone, the major ingredient in the smog engulfing major cities. High up in the stratosphere, ozone shields us from harmful ultraviolet (UV) rays. But at ground level, it irritates the respiratory system, causing coughing, choking, and reduced lung capacity. Children and the elderly are especially sensitive to smog. Urban ozone pollution has been linked to increased hospital admissions for respiratory problems such as asthma and to higher death rates on smoggy days, even at levels below the current standard (ATS 1996). Some studies suggest that longterm exposure to ozone may have chronic, irreversible impacts on lung function (Tashkin et al. 1994; Kunzli et al. 1997). Emphysema, chronic bronchitis, and chronic asthma may result from the permanent lung damage associated with repeated exposure to ozone (EPA 2000). Particulates (Soot) Diesel trucks and other motor vehicles emit particles (also known as particulates, particulate matter, or soot and abbreviated PM) directly from their tailpipes. They also release pollutants, notably nitrogen oxides and hydrocarbons, that form secondary particles in the atmosphere. Particulates irritate the eyes and nose and aggravate respiratory problems. Children, the elderly, asthmatics, and people with heart or lung disease are particularly at risk from exposure to particulates (EPA 1997a). Fine particles, those smaller than 2.5 microns 2 in diameter (PM 2.5 ), have also been directly associated with an increased risk of premature death (EPA 1996; ATS 1996). In one recent study, researchers followed more than 8,000 people in six different locations for 17 years. They found that the risk of premature death in areas with high levels of fine particles was 26 percent greater than in areas with lower levels (Dockery et al. 1993). Based on extrapolations from a larger study of premature mortality and particulates, the Environmental Protection Agency (EPA) estimates that its new health standards for PM 2.5, which will go into effect within the decade, will save 15,000 lives each year (EPA 1997a). At present, the specific mechanism by which fine particles increase the risk of death is unknown (EPA 1996). As a result, while regulations are based on the total mass of particles less than 10 or 2.5 microns, other characteristics such as particle size, surface area, number, chemical composition, or physical shape may also be important (Sawyer and Costantini 1997). For example, smaller particles especially ultrafines and nanoparticles (Table 2) more readily evade the body s physical defenses, penetrating further into the lungs, and are thought to cause more health 2 A micron, or micrometer, is one-millionth of a meter. The average human hair is about 100 microns thick.

5 5 ~ damage (ATS 1996). As a result, control strategies that focus solely on reducing the total mass of particles may not reduce public health risks proportionally. Carcinogenesis Public health agencies consider diesel exhaust a potential human carcinogen (Table 3). 3 Studies of people routinely exposed to diesel exhaust indicate 3 Although diesel exhaust contains over 40 compounds thought to cause cancer (CalEPA 1998a), most public health studies of diesel exhaust have focused on the aggregate emissions rather than on specific compounds. In its recent ruling, however, the California Air Resources Board voted to list only diesel exhaust particulates as toxic, rather than whole diesel exhaust, which contains both particulates and vapor-phase emissions (CARB 1998).

6 6 UNION OF CONCERNED SCIENTISTS a greater risk of lung cancer. For example, occupational health studies of workers exposed to high levels of diesel exhaust over many years, such as those in the railroad, dock, trucking, and busing industries, consistently demonstrate a 20 to 50 percent increase in the risk of lung cancer or death (HEI 1995; Bhatia et al. 1998). Even at the average rates of exposure most people experience, diesel exhaust poses a potential cancer risk. Estimates that extrapolate from epidemiological studies suggest that, at current exposure levels, as many as 450 of every million Californians (i.e., over 14,000 residents) are at risk of contracting lung cancer as a result of lifetime exposure to diesel exhaust. 4 One estimate suggests that 125,000 people may be at risk nationwide (STAPPA/ALAPCO 2000). Risk from diesel exhaust may be particularly high in cities, where large numbers of people are exposed to truck and bus pollution. In the Los Angeles region, for example, diesel particles account for an estimated 71percent of total cancer risk (SCAQMD 1999). Global Warming Diesel exhaust not only threatens public health, it contributes substantially to global warming through emissions of carbon and other heat-trapping gases. Transportation is the source of roughly one-third of all heat-trapping gases released in the United States. This is more than most countries release from all sources combined. 5 Each gallon of diesel fuel burned in a diesel truck engine results in emissions of 22.8 pounds of carbon and other heat-trapping gases. 6 An additional 5.4 pounds of heat-trapping gases result from the production and delivery of each gallon (Wang and Huang 1999). Nationally, heavy trucks emit nearly 400 million metric tons of heat-trapping gases annually, accounting for about 6 percent of US carbon emissions. 7 Heat-trapping emissions from transportation and other sources primarily those that burn fossil fuels have led to an increase in the earth s temperature. The global average surface temperature has increased by 0.5 F to 1.1 F since the last half of the nineteenth century, and all of the 10 warmest years on record have occurred in the last 15 years (UCS 1997). Over the next century, further unchecked increases in the atmospheric concentrations of carbon dioxide and other heat-trapping gases (such as methane and nitrous oxide) will cause more 4 The independent Scientific Review Panel of the California EPA has proposed a reasonable estimate of cancer risk from diesel exhaust to be for every microgram of diesel exhaust per cubic meter of air ( (µg/m 3 ) -1 ) (CalEPA 1998b). The current average exposure rate is 1.5 µg/m 3, resulting in an average lifetime risk of Only China, Russia, and Japan have higher total emissions (based on Marland et al. 1996). 6 Measured as carbon dioxide-equivalent emissions. Emissions of nitrous oxide and methane are added to carbon dioxide emissions based on the global warming potential of those gases. 7 UCS estimate based on energy use for freight trucks and total carbon estimate from the Annual Energy Outlook (EIA 2000).

7 7 extreme changes in global climate patterns. Scientists project a further increase in global average surface temperature of about 1.8 F to 6.3 F by the year 2100 (UCS 1997). Global warming will not mean more pleasant temperatures. Even within the next 20 years, different regions of the world will likely see longer droughts, more coastal flooding, and more frequent extreme weather events (UCS 1997). And if global warming continues, we could well see increased risk to human health, severe stress on large areas of forest, a loss of mountain and coastal-wetland habitats and the plants and animals that live there the expansion of deserts, the disruption of agriculture, and a rise in sea level of anywhere from 6 to 37.5 inches above the current level with persistent coastal flooding. Increased global warming will also affect fisheries, water resources, and all natural habitats. Human well-being, including commerce and economic development, could well be at risk. The most serious impacts will most likely include human health, agriculture, and natural habitats (UCS 1997). Higher surface temperatures could also increase the frequency of ozone-conducive meteorological conditions (Deul et al. 1999), making it more difficult and expensive to achieve and maintain clean and healthy air.